A vane-type machine of said type is known from U.S. Pat. No. 6,684,847 B1. The vanes are equipped, on both axial ends, with projections which are each guided in grooves provided in the stator. The profile of the grooves determines the movement of the vanes.
A vane-type machine of said type may be used for example as a booster pump in a reverse osmosis installation, and then acts as a water-hydraulic machine. In a refinement that has been used up until now, the rotor is mounted eccentrically with respect to the inner circumference of the stator. Then, during one rotation, a point on the surface of the rotor approaches the inner circumference once, until a minimum spacing is reached, and then moves away from the inner circumference again, until a maximum spacing is reached. If the vane-type machine is used as a pump, then an outlet opening for the respective working chamber is provided in the region of the minimum spacing, from which working chamber water can then be discharged at an elevated pressure. If the vane-type machine is used as a motor, then a feed or supply port is situated in said region, at which feed or supply port water can be fed in under pressure.
In the case of a vane-type machine of said type, it has hitherto always been the case that an even number of vanes has been used, and a spacer has been installed between vanes which are situated diametrically opposite one another, such that two mutually diametrically oppositely situated vanes have always described precisely one diameter. However, such a solution is possible only in the case of machines in which the inner circumference of the stator has a cylindrical shape.